This was followed by James Clerk Maxwell, who proposed in that light was an electromagnetic wave. In his theory of electromagnetism, the speed of light was represented as c.
And then in , Albert Einstein proposed his theory of Special Relativity , which postulated that the speed of light c was constant, regardless of the inertial reference frame of the observer or the motion of the light source.
By , after centuries of refined measurements, the speed of light in a vacuum was calculated at ,, meters per second. Ongoing research also revealed that light travels at different wavelengths and is made up of subatomic particles known as photons, which have no mass and behave as both particles and waves.
As already noted, the speed of light expressed in meters per second means that light travels a distance of 9,,,, km or 5,,,, miles in a single year. For example, the nearest star to Earth Proxima Centauri is roughly 4. The center of the Milky Way Galaxy is 26, light-years away, while the nearest large galaxy Andromeda is 2.
And the Cosmic Microwave Background , the relic radiation which is believed to be leftover from the Big Bang, is located some The discovery of this radiation not only bolstered the Big Bang Theor y, but also gave astronomers an accurate assessment of the age of the Universe.
This brings up another important point about measuring cosmic distances in light years, which is the fact that space and time are intertwined. As a result, looking at objects billions of light-years from Earth is to see billions of light-years back in time. Yes, light travels at an extremely fast speed. But given the sheer size and scale of the Universe, it can still take billions of years from certain points in the Universe to reach us here on Earth.
Hence why knowing how long it takes for light to travel a single year is so useful to scientists. Most passenger planes top out at approximately mph. Air Force, hit 4, miles per hour. The size and payload of a spacecraft also determine its maximum velocity.
A small, uncrewed spacecraft such as New Horizons , which is currently near Pluto, can travel at over 36, miles per hour; it arrived at its destination in less than a decade. But if it wanted to head to Alpha Centauri, the trip would take another 80, years. Still, there are ways we can dramatically improve our propulsion systems to decrease travel time. While this approach remains theoretical for now, its successful implementation could get crews to Mars in weeks, rather than seven to eight months, or a spacecraft to Alpha Centauri in about 30 years.
One idea common in science fiction is placing place crew members in a state of suspended animation for the long trip and then reawakening them upon arrival. But those bring challenges too. Nine weeks later, the Wright Brothers made history. Remember that the next time that you see a Hubble image that shows a host of galaxies dancing across the cosmos—what you are looking at is amazingly far away.
The time that it takes us to travel one light-year is unsurprisingly considerably longer than a year. In fact, it takes between six months and a year just to reach Mars, which is only And it took New Horizons nearly a decade to make its way from Earth to Pluto, which is just around the corner, 4. Even if we hopped aboard the space shuttle discovery, which can travel 5 miles a second, it would take us about 37, years to go one light-year.
The worst thing? The closest star, Proxima Centauri, is more than four light-years away. Care about supporting clean energy adoption?
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